In order to detect defects in a surface of a workpiece with high-reflectivity or to measure a size of the workpiece, a common method is to spray the surface of the workpiece with extinction powders for reducing the reflectivity. After the surface defects and the size are shown, the surface of the workpiece is inspected or measured by way of non-contact imaging technique. However, in such method, the extinction powders must be completely removed after inspecting and measuring, and thus it is very time-consuming and difficult, and easily leads to pollution of the production line. Accordingly, it is difficult to be widely used.